Bonding of articular cartilage using a combination of biochemical degradation and surface cross-linking |
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Authors: | Carsten Englert Torsten Blunk Rainer Müller Sabine Schulze von Glasser Julia Baumer Johann Fierlbeck Iris M Heid Michael Nerlich Joachim Hammer |
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Institution: | Department of Trauma Surgery, University Medical Centre Regensburg, Franz-Josef-Strauss-Allee, 93053 Regensburg, Germany. carsten.englert@klinik.uni-regensburg.de |
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Abstract: | After trauma, articular cartilage often does not heal due to incomplete bonding of the fractured surfaces. In this study we
investigated the ability of chemical cross-linkers to facilitate bonding of articular cartilage, either alone or in combination
with a pre-treatment with surface-degrading agents. Articular cartilage blocks were harvested from the femoropatellar groove
of bovine calves. Two cartilage blocks, either after pre-treatment or without, were assembled in a custom-designed chamber
in partial apposition and subjected to cross-linking treatment. Subsequently, bonding of cartilage was measured as adhesive
strength, that is, the maximum force at rupture of bonded cartilage blocks divided by the overlap area. In a first approach,
bonding was investigated after treatment with cross-linking reagents only, employing glutaraldehyde, 1-ethyl-3-diaminopropyl-carbodiimide
(EDC)/N-hydroxysuccinimide (NHS), genipin, or transglutaminase. Experiments were conducted with or without compression of
the opposing surfaces. Compression during cross-linking strongly enhanced bonding, especially when applying EDC/NHS and glutaraldehyde.
Therefore, all further experiments were performed under compressive conditions. Combinations of each of the four cross-linking
agents with the degrading pre-treatments, pepsin, trypsin, and guanidine, led to distinct improvements in bonding compared
to the use of cross-linkers alone. The highest values of adhesive strength were achieved employing combinations of pepsin
or guanidine with EDC/NHS, and guanidine with glutaraldehyde. The release of extracellular matrix components, that is, glycosaminoglycans
and total collagen, from cartilage blocks after pre-treatment was measured, but could not be directly correlated to the determined
adhesive strength. Cytotoxicity was determined for all substances employed, that is, surface degrading agents and cross-linkers,
using the resazurin assay. Taking the favourable cell vitality after treatment with pepsin and EDC/NHS and the cytotoxic effects
of guanidine and glutaraldehyde into account, the combination of pepsin and EDC/NHS appeared to be the most advantageous treatment
in this study. In conclusion, bonding of articular cartilage blocks was achieved by chemical fixation of their surface components
using cross-linking reagents. Application of compressive forces and prior modulation of surface structures enhanced cartilage
bonding significantly. Enzymatic treatment in combination with cross-linkers may represent a promising addition to current
techniques for articular cartilage repair. |
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